Disclosed are systems, methods and techniques for determining or inferring a status or fault for a portion or aspect of a global navigation satellite system (GNSS). For example, fault messages may be received from multiple mobile devices where fault messages provide indicators indicative of events or conditions. Fault indicators in received fault messages obtained from messages received from two or more of the mobile devices may be combined to infer a status or fault of at least a portion of a GNSS. Augmentation parameters conveying information related to an inferred fault may be transferred to a mobile device to improve GNSS location of the mobile device.